(a) Field of the Invention
The present invention relates to a non-aqueous type resin dispersion useful for a liquid developer for electrostatic photography, paints, printing inks, adhesives and the like.
(b) Description of the Prior Art
The resin dispersions used for a liquid developer for electrostatic photography, paints, inks and the like have normally been prepared by dispersing separately prepared resins such as alkylphenol, rosin-modified phenol resin, rosin-modified alkyd resin, maleic resin and the like in a solvent comprising a petroleum aliphatic hydrocarbon or its halide in the case of a developer, and in an aromatic hydrocarbon solvent in the case of a paint or ink.
The resin dispersion of this sort is demanded to have the following properties (1) the viscosity and fluidity are proper, (2) the dispersion stability and preservability to pigments are superior, (3) the coated film is lustrous and superior in adhesive strength, (4) the coated film dries quickly, and the like. However, conventional resin dispersions could not satisfy these requirements completely. Improvement in the performance of resin dispersions has been long-awaited.
In particular, the toner in the usual liquid developer for electrostatic photography includes a problem that although said toner normally functions to cause electrophoresis in response to the electric charge of an electrostatic latent image formed on the surface layer of an electrophotographic sensitive material or electrostatic recording material and form an image attached to that portion in a developing step, its resin and polarity control agent diffuse in a carrier liquid with the lapse of time to cause aggregation and make the polarity indistinct to thereby markedly deteriorate the image quality, in particular image density in the usual liquid developer, and other problems that since the adhesive strength of the toner (namely, the fixing strength of the image) is weak, the reslting image can be erased with an eraser, that when it is used for a color electrophotography, 4 colors such as yellow, red, blue and black can not overlap uniformly due to lack of transparency of the toner, thereby making the faithful color regeneration impossible, that when an image is formed on a zinc oxide sensitive paper and offset printing is effected by the use of same as an offset master, the number of durably printed sheets is not many and printing is not stable, and the like.